This invention is directed to a low density absorbent open-cell thermoplastic foam that is flexible and resilient. The foam is useful to produce a wide variety of personal care, health and medical care products.
Previous attempts to foam thermoplastic materials using thermoplastic elastomer, such as styrene block copolymer, often have not yielded low density open-celled materials. The properties of low density have been enhanced using a crosslinking agent which crosslinks the materials during extrusion. The crosslinking substantially hardens the foam and requires additional processing skills. Also, the possible existence of residual crosslinking agent makes this process less desirable for foams used in personal care, health and medical care products, which contact the human skin.
PCT International Publication WO 02/18482 discloses a thick extruded open-cell foam formed of a composition consisting of 4.5-75 parts by weight ethylene ionomer resin, 0.5-3.0 parts by weight polyolefin resin having a melting point exceeding 120° C., and 20-95 parts by weight of one or more polymers selected from the group of ethylene-propylene rubbers, styrene elastomers and polyethylene resins having a melting point of 120° C. or lower, wherein the foregoing polymers add up to 100 parts by weight. The foam is useful for packaging material, bags, fruit trays and other containers, and has shock absorption properties. While the described foam has flexibility, it possesses enough rigidity for these applications. Also, while the described foam may absorb some water, due to its open-cell structure, water absorption is not a primary function.
There is a need or desire for a low density, flexible, resilient, absorbent open-cell thermoplastic foam suitable for use in personal care, health and medical care products, many of which require softness and absorbency as primary features.